Electroanalgesic therapies are known nonpharmacologic alternatives to conventional analgesic drugs for the management of acute and chronic pain. For example, percutaneous electrical nerve stimulation (PENS) is a known form of electroanalgesic therapy typically used for the treatment of intractable pain associated with chronic low back pain syndrome by stimulating the spinal cord using electrodes implanted percutaneously into the epidural space. The term PENS has also been used to describe a technique for inserting 32-gauge acupuncture needles into soft tissues or muscles to electrically stimulate peripheral nerve fibers in the sclerotomal, myotomal, or dermatomal distribution corresponding to a patient's pain symptoms. Medical devices having arrays of percutaneous electrodes that utilize microstructure needles, which are less invasive than deeper-penetrating acupuncture needles, have also been used for delivering PENS. The microstructure needles provide sufficient penetration to overcome the electrical impedance of the skin tissue for effectively recruiting sensory fibers.
As the understanding of the topographical organization of nociceptive systems becomes more detailed, the target location of the stimulation, the percutaneous electrodes' depth of penetration, and the current amplitude become more exacting. Percutaneous neuromodulation therapy (PNT) and cutaneous field stimulation (CFS) are specific forms of PENS that have been developed using that understanding. PNT is used for the treatment of cervical and lumbar pain and utilizes longer, acupuncture-type needles having a depth of penetration into the skin tissue of up to 3 cm. And, CFS is used more generally to treat pain and itch and utilizes an array of microstructure needles introduced close to the nerve endings in the skin. Because of the stringent requirements established for needle electrodes by the Food and Drug Administration (FDA) regarding the packaging, sterilization, reuse, and disposal of such electrodes, treatments utilizing such electrodes have generally been administered under the supervision of a physician (e.g., in a doctor's office or a clinic).
CFS is used to assist in the management of chronic nociceptive and neuropathic pain based on the understanding that specific types of sensory nerves that are linked to diminishing the perception of pain can be activated by low amplitude, long duration electrical stimulation if electrodes having sharp tips (i.e., microstructure needles) are introduced close to the nerve endings in the skin. CFS treatment also influences specific active components necessary for perceiving itch by inducing long lasting inhibitory mechanisms in central pathways and by actually normalizing the number of epidermal sensory fibers in itchy skin. Accordingly, CFS also provides an alternative to known treatments for localized itch.
The sensory receptors stimulated by CFS are axons within the skin tissue known as nociceptors, specifically Aδ and C nerve fibers. The stimulation of Aδ and C nerve fibers, although effective in diminishing the perceptions of both pain and itch, can be a relatively uncomfortable treatment because a prickling and/or burning sensation is perceived from the stimulation of the Aδ and C nerve fibers, which can be painful. Because the aversiveness of Aδ and C nerve fiber stimulation can be masked by Aβ fiber stimulation, it would be a considerable advantage to combine Aβ fiber stimulation (e.g., transcutaneous electrical nerve stimulation (TENS)) and Aδ and C fiber stimulation (e.g., CFS) in the same equipment. Accordingly, there is a need for a method and device that combines Aβ fiber stimulation and Aδ and C fiber stimulation in one treatment. Moreover, there is a need for a method and device that combines TENS and CFS in one treatment.